Ceramic honeycomb structures are widely used as anti-pollutant devices in engine exhaust systems, such as catalytic converter substrates in automobiles, and diesel particulate filters in diesel-powered vehicles. In these applications, the ceramic honeycomb structures are comprised of a matrix of ceramic webs, or walls, which define a plurality of cells or cell channels. The web matrix is typically surrounded by a skin layer. In filters, at least some of the channels are sealed by plugs, such as to force the exhaust to flow through the ceramic webs.